Process for producing alkylated tars

ABSTRACT

A PROCESS FOR THE PRODUCTION OF ALKYLATED TARS COMPRISING REACTING A LOWER OLEFIN, IN THE PRESENCE OF A SILICAALUMINA OF ZEOLITE TYPE CATALYST, WITH A TAR FRACTION OBTAINED BY THE THERMAL DECOMPOSITION OF A PETROLEUM HYDORCARBON AT 700-2300*C., AND IF DESIRED, FOLLOWING A DESULFURIZATION REACTION.

United States Patent Ofice Patented May 16, 1972 ,663,428 PROCESS FORPRODUCING ALKYLATED TARS Masaaki Takahashi, Tokyo, and Osamu Mayumi,Chiba, Japan, assignors to Kureha Kagalru Kogyo Kabushiki Kaisha, Tokyo,Japan No Drawing. Filed Feb. 16, 1970, Ser. No. 11,904 Claims priority,application Japan, Feb. 14, 1969, 44/ 10,488 Int. Cl. C10g 37/00 US. Cl.208-97 5 Claims ABSTRACT OF THE DISCLOSURE A process for the productionof alkylated tars comprising reacting a lower olefin, in the presence ofa silicaalumina or zeolite type catalyst, with a tar fraction obtainedby the thermal decomposition of a petroleum hydrocarbon at 700-2300 C.,and if desired, following a desulfurization reaction.

BACKGROUND OF THE INVENTION Field of the invention After extensivestudies of the properties and utilization of tar fractions obtained bythe high temperature cracking of petroleum oil, the present inventorshave now found that these tar fractions comprise polycyclic aromaticcompounds having extremely few side chains, and that any impuritiesinitially contained in the petroleum oil, such as sulfur, nitrogen,metal, etc. are converted into gas or pitch during thermal crackingthereby leaving a tar fraction having a greatly reduced impurity level.After investigating methods of reacting these tar fractions witholefins, we have accomplished the present invention.

The tar fraction presently employed is obtained from the heavy crackingoil obtained by thermally cracking petroleum hydrocarbons at atemperature above 700" C. and below 2300 C., and subsequently removingsolid pitch from the heavy cracked oil, and which consists of a fractionboiling at 200 C.-500 C., calculated at normal pressure.

The structure of these fractions are determined by gas chromatography,infrared absorption analysis, nuclear magnetic resonance analysis, massspectrograph etc. It has been found that the main component structure ofthe fractions consists mainly of from two to five benzene nuclei,particularly from two to four condensed benzene rings having short sidechains, such as methyl groups, attached thereto, i.e., polycyclicaromatic compounds substantially free from side chains.

This structure differs from that of petroleum asphalt, usually calledtars, and also from that of coal tar obtained by the dry distillation ofcoal, by the following points:

Petroleum asphalt consists of a mixture of polycyclic aromatic compoundshaving a plurality of long alkyl side chains, long chain parafiiniccompounds and naphthenic compounds having aromatic or alkyl groupsattached thereto; due to the fact that petroleum asphalt does notundergo a heat treatment at a high temperature, as is the case with thepresent invention.

On the other hand, coal tar is highly aromatic and resembles the tarfraction of this invention, since it undergoes a heat treatment at hightemperatures, but it contains greater amounts of impurities, i.e.,oxygen, sulfur, nitrogen metals etc., and has more of a heterocyclicstructure in the coal than is contained in petroleum oil.

Thus, the tar fraction utilized in the present invention is clearly aspecial type of tar. The alkylated tar products of this invention areunique and can be obtained only by reacting a lower olefin with theabove-described tar fraction.

SUMMARY OF THE INVENTION The present invention provides a process forproducing alkylated tars by reacting a lower olefin with certain tarfractions, in the presence of a silica-alumina or zeolite type catalyst;the tar fractions being polycyclic aromatic compounds produced by thethermal decomposition of petroleum hydrocarbons at a temperature of from700 to 2300 C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the process of thisinvention, the thermal cracking of the petroleum hydrocarbons mayinvolve flame cracking, high temperature steam cracking, coil cracking,sand cracking etc., that is, any process by which the feed petroleum oilis thermally cracked at a temperature above 700 C. and below 2300 C. toform acetylene and olefins such as ethylene, propylene, butylene,together with heavy cracking oil formed as a byproduct.

The particular petroleum hydrocarbon employed includes any type readilyavailable in industry such as gaseous hydrocarbons, naphtha, light oil,heavy oil, residual oil, mixtures thereof, and crude oil.

The tar fractions to be used are those obtained from the heavy crackingoil after removing solid pitch therefrom, and which have a boiling pointof from 200 to 500 0., calculated at normal pressure, preferably from250 C. to 450 C. This fraction exhibits a hydrogen to carbon atomicratio (H/C) of from 0.5 to 1.0, and a specific gravity of from 1.0 to1.3.

The feed olefin is a lower olefin generally having a carbon number ofnot higher than 8, preferably those having from 2 to 4 carbon atoms.Typical olefins to be used are therefore ethylene, propylene andbutylene. The use of these last-mentioned olefins is economicallyadvantageous.

Prior to the reaction of the olefin with the tar fraction it isdesirable to desulfurize the tar fractions, if necessary, in order tomarkedly prolong the catalyst life during the alkylation.

The desulfurization may be conducted in a conventional desulfurizingapparatus and is operated by reacting hydrogen with the tar fraction inthe presence of a catalyst to thereby remove sulfuric compounds in thetar fraction as hydrogen sulfide. The catalyst employed in thedesulfurization may contain cobalt, molybdenum or nickel in the form offree metal, oxides, sulfides or combinations thereof, supported by asuitable carrier such as silicaalumina. The desulfurizing reaction iscarried out at a temperature of 350-450" C., under a pressure of 20-100kg./cm. using a feed ratio (molar ratio of hydrogen to the tarfractions) of 3-15 mole/mole and at a liquid hourly space velocity(L.H.S.V.) of 05-10 cc./cc.-catalyst/hr. Under such conditions, thedesulfurization reaction takes place readily while attaining a gooddesulfurizing effect.

The alkylation reaction is conducted by mixing the gaseous olefin withthe tar fraction which has been (or has not been) previouslydesulfurized, and passing the mixture over a solid catalyst bed underspecified reaction conditions. The alkylation apparatus may be aconventional fixed bed type reactor. The reaction conditions will bemore fully described below.

The catalyst to be used is preferably a solid acid type catalystincluding, for example, silica-alumina, or a group III-B metal of thePeriodic Table such as lanthanum (La), cerium (Ce), thorium (Th) etc.supported on a zeolite carrier.

The reaction takes place more rapidly as the temperature is increased,but the inverse reaction and a polycondensation reaction will begin totake place at a temperature exceeding a certain limit, so that there ismaximum reaction rate depending upon the temperature. The rate alsoincreases as the pressure is increased from atmospheric tosuperatmospheric, but a polycondensation reaction takes place at apressure exceeding a certain limit. Further, the ratio of feedcomposition influences the degree of alkylation. As the olefinztarfraction ratio increases, the degree of alkylation becomes larger; i.e.,the mole numbers of olefin reacting per mole of tar frac tion. Usually,excess olefin is fed to the system and unreacted olefin may be re-usedby recycling it. The liquid hourly space velocity (L.H.S.V.) is theliquid volume of flowing tar fraction per unit hours per unit catalystvolume, and the decrease of L.H.S.V. from a higher to a lower value willincrease both the reaction conversion and the degree of alkylation butwill reduce the product yield.

As a result of the above considerations, it is economically advantageousto set the preferred reaction conditions as follows: a temperaturebetween 250 C. and 380 C., a pressure between 1 and 50 kg./cm. a feedratio between 0.2 and 10, and a L.H.S.V. between 0.1 and 50cc./cc.-catalyst/hr. The degree of alkylation is varied by varying theL.H.S.V. while the length of the alkyl group in the tar fraction isvaried by varying the particular olefin fed into the system. Under theabovementioned reaction conditions, neither the decomposition nor thepolycondensation reaction occurs and the loss in material balance isminimal. Moreover, the decrease in catalyst activity due to carbondeposition is greatly minimized so that the catalyst may be used over aprolonged period.

The alkylated tar thus formed has a lower specific gravity and a lowerrefractive index as well as a higher H/C, viscosity, average molecularweight and boiling point than that of the feed tar fraction. By analysisof the alkylated product utilizing gas chromatography, infraredabsorption spectrum, nuclear magnetic resonance etc., the alkylated taris estimated to have a chemical structure consisting of condensedpolycyclic aromatic rings having from two to five, particularly from 2to 4, benzene rings, which are combined with alkyl groups having thesame carbon number as that of the olefin used in the reaction. Whenethylene, propylene or butylene is used as the olefin, the resultingalkylated tar has as its main component an ethylated, propylated orbutylated polycyclic aromatic compound, respectively.

As described, this invention provides a process for syntheticallyproducing novel alkylated tar fractions having various alkyl group sidechains, from polycyclic aromatic compounds substantially free from sidechains. Accordingly, various alkylated tars having desirable propertiescan be produced depending upon their desired uses.

The alkylated tar produced by the process of the present invention isused as an electric insulating oil, a rubber processing oil, a heattransfer oil, a plasticizer and as an intermediate material in organicsynthesis, etc. The present invention will be more fully illustrated byreference to the following examples, which are merely illustrative, andnot intended to be limiting, in nature.

Example 1.Petroleum naphtha was thermally cracked according to a flamecracking process at a temperature of 1200" C. for a contact period of0.003 second to obtain a heavy cracking oil from which a relativelylower boiling tar fraction having a boiling point of 250350 C.(calculated at normal pressure) was taken for use as a feed stock. Thephysical properties of this fraction were measured by gaschromatography, infrared absorption analysis, nuclear magneticresonance, mass spectrograph analysis, etc. in order to determine itschemical structure. The result of the analysis indicated that the tarfraction consisted mainly of aromatic compounds having two or threecondensed aromatic rings to which a few methyl side chains wereattached, and was substantially free from naphthenic and paraffiniccomponents. The other physical properties are given in Table 1 below.

Ethylene having a commercial grade purity of 99% was used as the olefinfeed. The reactor used was a stainless steel tube 1000 mm. in length and25 mm. in diameter. The catalyst used was granular silica-alumina (SiO87%, A1 0 13%). The reaction was started by preheating the tar fraction,without desulfurizing treatment, to 200 C., then mixing it with theethylene and passing the mixture to the reactor after adjusting the feedmolar ratio (ethylene to tar fraction) to 5. The reaction was carriedout at a reaction temperature of 300 C., a pressure of 30 kg./cm. and aliquid hourly space velocity (L.H.S.V.) of 0.25 cc./cc.-catalyst/hour.The reaction conditions and the properties of both the tar fraction andthe resulting alkylated tar are shown in Table 1 below. The degree ofalkylation, i.e., the mole number of added ethylene per mole of tarfraction, increases, as shown in Table 2, as the feed molar ratioincreases, and it also increases as the L.H.S.V. decreases as shown inTable 3. Thus, the degree of alkylation was controlled depending uponthe feed molar ratio and the value of L.H.S.V. During the course of theoperation, the reaction proceeded with ease without causing a decreasein catalyst activity. Though the ethylated tar so produced had somewhatof a deeper yellow-brown color than the feed tar, it could be convertedinto clear liquid after distillation or acidic clay treatment. Theethylated tar so obtained exhibited excellent electric insulatingproperties, i.e., in volume intrinsic resistance, dielectric constant,dielectric tangent, etc., and it was also found to have superior rubberprocessing properties, that is, as a plasticizer for polyvinyl chloride.Moreover, many organic compounds may be derived from the alkylated tarand hence it is a very useful substance.

TABLE I.REACTION 0F TAR FRACTION WITH ETHYLENE Feed Ethylation (1)Reaction conditions:

l Silica-alumina.

TABLE 2 Relation between food composition and alkylation degreetemperature 300 0., pressure 30 kg./cm. L.H.S.V. 0.25 ce,/ce.-cat./hr.Catalyst: silica-alumina Feed composition ratio (ethylene/tar fraction)mole/mole 0.2 1.0 5.0 10.0 Alkylation degree (reacted ethylene/tartraction) mole/mole 0. S5 2. 77 3. '15

TABLE 3 Relation between L.H.S.V. and alkylation degree temperature 300Cu pressure 30 kg./om. feed composition ratio 5:1 (ethylene/tar fractionmole/mole Catalyst: silica-alumina L.H.S.V. ec./cc.-cat.lhr 3. 30 1. 0.66 0.25 Alkylation degree (reacted ethylene/tar fraction mole/mole0.31 1. 65 1. 91 2. 77

Example 2.--Petroleum naphtha was thermally decomposed according to ahigh temperature steam cracking process at a temperature of 1,500 C. fora contact time of 0.002 second to form a heavy cracking oil from which arelatively high boiling tar fraction, boiling at 350-450 C. (calculatedat normal pressure), was collected and used as the feed material. Thereaction apparatus and the manner of operation were the same as employedin Example 1, and the reaction conditions and the properties of theproduct are given in Table 4. From these results, it is noted that theethylation reaction takes place readily when using a higher boiling tarin place of the lower boiling tar fraction as the feed.

TABLE 4.--REACTION OF TAR FRACTION WITH ETHYLENE Feed Ethylation (2) 1Silica-alumina Example 3.-Ceria crude oil was thermally decomposedaccording to a high temperature steam cracking process at a temperatureof 1000 C. for a contact time of 0.005 second to form a heavy crackedoil from 'which a wide ranged tar fraction, boiling from 250 to 450 C.,was collected and used as the feed. This tar had a somewhat highercontent of sulfur than the tar fraction obtained from the petroleumnaphtha, i.e., the former containing 0.224% by weight, and the lattercontaining 0.072% by weight, sulfur, so that the former tar fraction wasdesulfurized to a sulfur content of 0.001% by weight prior toalkylation. The alkylation was then conducted using an alkylationcatalyst containing 1.5% by weight of cerium supported on a zeolitecarrier. The reactor and operation were the same as in Example 1. Thereaction conditions and properties of feed and products are given inTable 5. From these results, it is noted that the alkylation reactiontakes place smoothly by using a ceriumzeolite catalyst as well, and thelife of the alkylation catalyst is extended by preliminarilydesulfurizing the crude tar which contains a relatively large amount ofsulfur compounds.

TABLE 5.REAC'1ION 0F ETHYLENE WITH DESULFURIZED TAR FRACTION Desulluri-Feed zation (3) Ethylatlon (4) Reaction conditions:

Catalyst Temperature C. 400 300 Pressure (kg/cm!) 3 50 31 Feedcomposition (OZHi/tfll fraction) mole/mole 2. 5 5 L.H.S.V.,cc./cc.-eat.lhr 5 1.0

P iff iii a b y ogen car on atomic ratio 0.80 0. 94 Alkylation degree(reacted Cilia/tar fraction) mole/mole 2. 25 Specific gravity 1. 1181.049 Sulfur (percent by weight) 0. 224 0.001 0 1 CO-MO-AleOa.Ce-Zeolite.

Example ip-Using the feed tar fraction of Example 1, the alkylation wasconducted with propylene. The reactor and operation were the same as inExample 1. The reaction conditions and the properties of feed andproduct 5 are given in Table 6 ,(reaction No. (5)). This shows that theprocess of this invention can be readily performed using propylene aswell as ethylene.

Example 5.The tar fraction used in Example 1 was alkylated with butylene(mixture of butylene-1 and butylene-2). The reaction apparatus andoperation were the same as in Example 1, except that a different olefinwas employed as the starting material. The reaction conditions and theproperties of the material and product are shown in Table 6 (reactionNo. 6)). It is obvious from the results obtained that the alkylation ofthe tar fraction with butylene also proceeds easily.

TABLE 6.THE REACTION OF TAR FRACTION WITH PROPYLENE AND BUTYLENE FeedReaction conditions:

Olefin Catalyst p Temperature C. 300 300 Pressure (kg/cm!) 40 50 Feedcomposition (olefin/tar fraction) mole/mole 5 5 L.H .S.V.,cc./cc.-cat./l1r 1. 5 3 Properties:

H/C (hydrogen/carbon atomic ratio) 0.85 1.75 1. 47 Alkylation degree(reacted olefin/tar) m0le/m0le 2. 10 1. 55 Specific gravity (15 C.) 1.071 1. 012 1.002 Refractive index (25 0.)- 1. 6363 1. 6105 1.6013Viscosity (20 0.) cp 12.2 150 180 50% boiling point (calculated asnormal pressure C.) 304 390 395 1 Propylene. 2 Butylene. BSilica-alumina.

Example 6.Petroleum naphtha was thermally cracked at 800 C. for acontact time of 0.5 second to produce ethylene and propylene. A fractionhaving a boiling point of 250 C. to 350 C. was extracted from the bottomoil occurring as the byproduct during the thermal cracking procedure.The fraction obtained was desulfurized with a cobalt/molybdenum/aluminatype catalyst using the same apparatus as used in Example 3, and thenpropylated with propylene. The results obtained are shown in Table r e Iv 0 7, together with the reaction conditions.

TABLE 7 Desulfurization Propylation 50 Reaction conditions:

Catalyst Temperature C 400 300 Pressure (kg/0111. 50 40 Ratio ofpropylene to tar fraction (mol/mol) 2. 5 5 L.H.S.V.(cc./cc.-catalystlhr.) 5 1.5 Properties of the propylated product:

Degree of alkylatio 2. 2 Specific gravity ((14 1. 024 Refractive index(1 13 1.005 Viscosity (30 C est 17.4 Flow point -45 Ignition point C.)155 l Cobalt/molybdeuum/alumina. 2 Silica-alumina.

What is claimed is:

1. A process for the production of alkylated tar which comprises:

(a) cracking petroleum oil in a thermal reaction at a temperature offrom 700 C. to 2,300 C. to obtain a fraction having a boiling point atnormal pressure of from 200 C. to 500 C., having a hydrogen to carbonatomic ratio of 0.5 to 1.0, having a specific gravity of 1.0 to 1.3 andhaving chemical structure consisting essentially of polycyclic aromaticcompounds substantially free from side chains;

(b) desulfurizing said fraction with hydrogen in the presence of adesulfurizing catalyst at a temperature in the range of 350-450 C. and apressure of 20-100 kg./cm. and

(c) alkylating said desulfurized fraction with a lower olefin of 2 to 4carbon atoms in the presence of an alkylation catalyst selected from thegroup consisting of silica-alumina catalyst and zeolite catalyst.

2. A process as in claim 1 wherein said alkylation catalyst comprises azeolite' support having catalytic material comprising a Group III-Bmetal thereon.

3. A process as in claim 1 wherein said desulfurization is conducted ata feed ratio of moles of hydrogen to moles of tar fraction of from 3 to15 and at a liquid hourly space velocity of from 0.5 to 10cc./cc.-catalyst/ hour.

4. A process according to claim 1 wherein said alkylation is carried outat a temperature from 250 to 380 C., at a pressure from 1 to 50 kg./crn.with the liquid hourly space velocity of said tar fraction being from0.1 to 50 UNITED STATES PATENTS 2,604,494 7/1952 Morris et a1 260671 B2,645,672 7/1953 Schulze 260671 B 3,437,702 4/1969 Kirk, Jr., et al.260-671 R 3,277,018 10/1966 Plank et a1. 260671 R DELBERT E. GANTZ,Primary Examiner G. J. CRASANAKIS, Assistant Examiner US. Cl. X.R.260-671 G, 671 P

